Slurry for CMP

TABLE 14.2 Pads and Slurries for CMP of Characteristic Materials in Microfabrication. 

In this chapter, we described the role of each component in CMP slurry, and discussed the characterization of slurries for CMP. Since CMP was developed in the 1980s, many researchers have investigated CMP slurries in a variety of ways. However, there is still a need to understand more profoundly how the slurry characteristics affect CMP performance. These issues can be solved through a fundamental study of powder technology, surface chemistry, and colloidal chemistry. 

CMP of different materials needs polishing slurries with different pH value, e.g., slurry for oxide CMP has a basic pH... 

The need for a reliable source of slurry during CMP stimulated the growth of a whole industry of bulk chemical distribution (BCD) systems. An extended discussion of BCD systems is beyond the scope of this work, but a few words are in order. Slurry distribution systems vary in sophistication from the simple laboratory system consisting of little more than a barrel of slurry and a pump to sophisticated delivery systems designed to supply slurry to tens of CMP tools in a high-volume production environment [56]. 

J. P. Bare, B. Johl, and T. A. Lemke, Comparison of Vacuum-Pressure vs. Pump Dispense Engines for CMP Slurry Distribution, Proceedings of SEMlCONtWesl Contamination in Liquid Chemical Distribution Systems Workshop (July, 1998). 

Li Y. CMP slurry developments.CMP for ULSI Multilevel Interconnection Short Course 2005 Fremont, CA (2005 with courtesy from P. LeFevre). 

FIGURE 2.1 Worldwide markets for CMP and post-CMP equipment, CMP slurries, CMP pads, and other consumables, 2003-2008 ( millions) (from Ref. 1). 

Dispersion stability is critically important for all CMP slurries. For example, particle-particle aggregation may significantly increase the mean particle size of a slurry and result in surface defects such as scratches and delamination. Severe aggregation can also accelerate the settling of slurry, which can drastically alter the physical and chemical characteristics of a slurry. Therefore, a proper dispersion of metal oxide or abrasive particles in an aqueous environment is fundamentally important for CMP applications [58]. One of the most effective and commonly used methods for the stabilization of a colloidal dispersion involves the use of surfactant. 

The added surfactant molecules intended for CMP slurry stabilization can adsorb not only onto the abrasive particle but also onto the surface of the wafer to be polished. Depending on the extent of such adsorption, the added surfactant may influence the CMP process in several ways such as change in friction behavior of the slurry, modification of removal rate and selectivity, alteration of defectivity level, and shift in post-CMP profile. In this section the impact of surfactant adsorption on the removal rate, selectivity, and post-CMP cleaning characteristics will be discussed. 

What steps would you take to design CMP slurry for low-k applications ... 

Surya Sekhar M, Ramanathan S. Characterization of copper chemical mechanical polishing (CMP) in nitric acid-hydrazine based slurry for microelectronic fabrication. Thin Solid Films 2006 504(l-2) 227-230. 

For CMP, material removal rate is only one of the many performance metrics. In most cases, the defect count is much more critical to the overall yield of a CMP process. As shown in Fig. 13.26a and b, the defect count has a stronger correlation with the D99 of a slurry than the D50. 

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